Police began investigating after Gregory, during taping of his Dec. 23 show, held up an object he said was a magazine that could hold 30 rounds.

He was interviewing National Rifle Association executive vice president Wayne LaPierre and used the magazine as a prop while discussing gun control.

D.C. gun laws generally restrict the possession of high-capacity magazines, regardless of whether the device is attached to a firearm. Police say they told NBC it would be illegal to possess the device.